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Abstract
In this study, performance of a full-scale combined treatment plant for oilfield wastewater from alkaline/surfactant/polymer flooding was investigated. The combined process consisted of chemical coagulation, hydrolysis/acidification, and bio-contact oxidation. The experimental results demonstrated that chemical coagulation treatment with polymeric ferric sulfate proved to be the most effective in removing the chemical oxygen demand (>80%) from the wastewater under the dosage of 600 mg/m3. The highest acidification efficiency in hydrolysis acidification tank was 25.8% at hydraulic retention time of 20 h. The average values of chemical oxygen demand, biochemical oxygen demand, oil, and NH3-N of the combined process could be reduced to 116, 19, 4, 11, and 20 mg/L, respectively. The final effluent could meet the class II national wastewater discharge standard of petrochemical industry of China.